The present invention generally relates to semiconductor processing and, more particularly, to a system and method for facilitating removal of defects from a substrate.
The tendency of semiconductor devices such as integrated circuits (IC) and large scale integrated circuits (LSIC) toward minuteness has rapidly progressed, and higher accuracy has been required of apparatuses for manufacturing such semiconductor devices. In particular, such requirements are demanded from exposure devices in which a circuit pattern of a mask or a reticle is superposedly transferred onto a circuit pattern formed on a semiconductor substrate. It is desired that the circuit pattern of the mask and the circuit pattern of the substrate be superposed one upon the other with accuracies of, for example, less than 0.1 xcexcm.
In order to remain competitive, semiconductor manufacturers continually strive to reduce costs associated with manufacturing semiconductor chips while at the same time improving yield in the manufacturing process. However, substrate defects typically result in a decreased yield and, in turn, provide associated increases in the manufacturing cost. Some defects exist, for example, on blank substrates as purchased. Other defects might be caused during manufacturing, such as by a process tool utilized during fabrication of the substrate. One particular type of defect is in the form of a contaminant particle that may adhere to the substrate during processing. Therefore, particle removal is a major issue in substrate surface preparation.
One factor to consider in the development of any cleaning method is to effectively overcome the forces in play between the substrate and the different foreign materials present on the surface of the substrate. Other relevant factors include mitigating deposition and redeposition of contaminants, mitigating damage to the substrate, and mitigating safety and environmental hazards.
Various methodologies exist for removing defects on substrate surfaces. Such methodologies are generally divided into two categories: wet-cleaning methods and dry-cleaning methods. Examples of wet-cleaning methods include: dissolving the foreign material in a solvent or aqueous solution; immersing the substrate in a solvent or aqueous solution to reduce Van der Waals forces; and providing a fluid flow across the substrate to provide a drag force on the particle, causing it to slide or roll off. Examples of dry-cleaning methods include: etching the substrate surface to dislodge the foreign material; using a vibration action to cause particle removal by liftoff; electrostatic attraction of charge particles to cause liftoff; and spinning the substrate to provide a centrifugal force that causes the particle to slide or roll off.
However, a substrate surface may be further contaminated by the cleaning method and the equipment used. This is possible by exposing the surface to contaminants in the chemicals, equipment, and environment used for cleaning or by making the surface highly susceptible to mechanisms by which redeposition is promoted after cleaning. Such redeposition may occur by failing to eliminate electrostatic and ionic charges on the surface.
As it becomes more and more difficult to adequately clean the substrate, cleaning methodologies are becoming more aggressive. For example, cleaning methods such as etching, chemical attacks, and mechanical force are being employed, which may damage a substrate during cleaning.
Wet-cleaning methods are conventionally employed more frequently than dry-cleaning methods. Also, wet-cleaning methods are easily applicable to the removal of particles and contamination above 1 xcexcm in size. However, as cleaning specifications become tighter, and the other factors such as deposition/redeposition, safety, and environmental requirements become more important, wet-cleaning becomes less advantageous. Further, water rinsing and the subsequent problems with drying, which are common to the liquid phase cleaning methods, are not encountered when employing dry-cleaning methods. In addition, as device densities continue to increase, it becomes more desirable to remove submicron and contaminants, which is difficult with wet-cleaning methods.
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is intended to neither identify key or critical elements of the invention nor delineate the scope of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later.
The present invention provides a system and method to facilitate the removal of substrate defects, such as contaminant particles. One aspect of the present invention utilizes a charge to loosen a defect relative to the substrates so that a defect removal system, such as a pump system, may be employed to remove the defect from the substrate. According to a particular aspect, an ionized gas is applied to the surface of the substrate to weaken the attractive forces between the defect and the substrate. As a result, the present invention is able to help produce a substrate of increased quality (e.g., fewer defects, less damage to the surface, etc.) comparable to situations when the present invention is not employed.
One aspect of the present invention provides a system for facilitating defect removal. The system includes a processing environment in which a substrate may be supported for processing. A source is operable to apply a charge toward a surface of the substrate for loosening at least one defect relative to the substrate. A defect removal system associated with the processing environment, in turn, removes the defect relative to the substrate.
Another aspect of the present invention provides a method of facilitating removal of a defect relative to a substrate. The method includes applying a charge to loosen the defect relative to the substrate and removing the defect relative to the substrate. According to one particular aspect, the charge may be applied via an ionized gas directed to a surface of a substrate as a beam.
To the accomplishment of the foregoing and related ends, certain illustrative aspects of the invention are described herein in connection with the following description and the annexed drawings. These aspects are indicative, however, of but a few of the various ways in which the principles of the invention may be employed and the present invention is intended to include all such aspects and their equivalents. Other advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.